High magnetic field homogeneity (for example, a difference between the maximum value and the minimum value of a magnetic field is several ppm or less) in an imaging space (field of view: FOV) near the magnetic field center is required for a magnetic field generation device mounted on a magnetic resonance imaging (MRI) apparatus. However, actually, the high magnetic field homogeneity is disturbed due to the influence of a manufacturing dimension error in a manufacturing stage of the MRI apparatus or the influence of magnetic bodies around a location where the MRI apparatus is provided.
Therefore, in the MRI apparatus, the homogeneity of magnetic field intensity in an FOV is finely adjusted (hereinafter, referred to as shimming). As an example of shimming, there is passive shimming in which shim pieces of correction magnetic bodies (hereinafter, referred to as magnetic pieces) are disposed around an FOV, and a static magnetic field distribution is finely adjusted. The passive shimming is a method of adjusting a static magnetic field distribution of an FOV to desired homogeneity by disposing an appropriate amount of magnetic pieces at an appropriate position through optimization computation (refer to PTLs 1 and 2). In other words, the homogeneity of the static magnetic field distribution of the FOV is adjusted by a magnetic field distribution generated by magnetic moment of the magnetic pieces disposed in a magnetic field.